This invention relates to a pager receiver which is capable of displaying alphanumeric symbols, such as numbers, characters, and the like. It should be noted here throughout the instant specification that such a pager receiver for displaying the alphanumeric symbols may be called merely a pager receiver for brevity of description.
A pager receiver of the type described comprises a display unit, such as a liquid crystal display (an LCD) unit, for displaying alphanumeric symbols, a display driver for driving the display device, and a read-only memory (an ROM) for storing display signals representative of the alphanumeric symbols.
With such a pager receiver, troubles and malfunctions sometimes take place in the display unit per se and the display driver. In order to detect the troubles and the malfunctions, a display test must be carried out either at the beginning or during operation of the pager receiver by transmitting a predetermined number of test patterns from a transmitting end to the pager receiver and by making the display unit visually display the test patterns. During the display test, all alphanumeric symbols should be displayed by the display unit. Otherwise, the display test does not make sense.
Inasmuch as the transmission of the test patterns must be carried out on the display test, an encoder of the transmitting end should be modified or changed in design when the test patterns are varied. In addition, a procedure for the display test becomes intricate as the number of the test patterns increase with an increase of the alphanumeric symbols.
However, all of contents, or the display signals stored in the ROM should be inspected or tested in order to be collated with desired signals. For this purpose, two methods have been implemented for inspection of the contents. A first one of the methods is to mechanically detach the ROM from the pager receiver so as to read the contents out of the ROM by the use of a code programmer as called in the art. The first method needs a long time to inspect the contents and inevitably reduces a reliability of the inspection, because the ROM is once detached from the pager receiver. In addition, the code programmer must be prepared on carrying out the inspection.
A second one of the methods is to inspect the contents of the ROM detaching the ROM from the pager receiver. With the second method, a plurality of key codes which are in one-to-one correspondence to the contents of the ROM are transmitted from the transmitting end to the pager receiver so as to make the display unit visually display the contents of the ROM. In order to display all contents of the ROM with the second method, a number of the key codes should successively be sent from the transmitting end to the pager receiver in question. The second method is therefore troublesome and needs a long time.